Patent GB-611305-A (GB)
Title: Improvements in or relating to fuel injection systems for internal combustion engines
IPC: F02D1/00
Filed: 1944-10-06
Abstract: 611,305. Fluid-pressure servomotor-control systems. BENDIX AVIATION CORPORATION. Oct. 6, 1944, No. 19245. Convention date, Feb. 13, 1943. [Class 135] [Also in Groups XXVII and XXVIII] In a fuel injection system for internalcombustion engines comprising a regulating device for varying the air supply through a conduit, an injection pump with several pumping members for supplying the respective engine cylinders, and a further regulating device to vary the effective pumping capacity of the members, one of the regulating devices is manually actuated and the other is operatively connected to a movable wall such as a diaphragm to which fuel is supplied at a variably controlled pressure. In the arrangement shown in Fig. 1, the air flow to the engine cylinders 19 is controlled manually by a throttle 15 and the fuel injection pump 31 is controlled automatically to govern the flow of fuel in accordance with the air flow. Air enters by the scoop 12 and passes through venturis 13, 14 to the supercharger 17 and thence by passages 18 to the engine. The fuel supply is drawn from a tank 26 and passes by a pipe 27 to a handoperated wobble pump 40 and on to an engine driven pump 38 which supplies fuel to a regulator unit 28. From the regulator 28, fuel passes through a metering unit 29 and thence by a pipe 30 to the pump 31. The pump is driven from the engine through gears 34, 35 and its capacity is regulated by means connected to a diaphragm 46 exposed on one side to the fuel pressure in the pump casing and on the other by a pipe 48 to the pressure in the small venturi 13 or to atmosphere or to any other desired pressure. Pipes 32 leading from the pump discharge directly into the cylinders 19 as at the nozzle 33 or into the passages 18 adjacent the inlet valves 20. The pump 31 is fitted with an accelerator pump 52 connected by a pipe 53 to a point downstream of the throttle 15. Pipes 41, 42, 43 lead air and fuel vapour back to the tank 26. The regulator 28 and the metering unit 29 are shown in section in Fig. 2. The former comprises a main fuel control valve 68 with a balancing diaphragm 69 and balancing passages 74 and an arrangement of four diaphragms 63, 64, 65, 66 on a rod 67 secured to the valve 68. The diaphragm 63 separates an unmetered fuel chamber 56 from a metered fuel chamber 57 and is acted on by a pressure difference which is a measure of the rate of fuel flow. The diaphragm 65 separates two chambers 58, 59, the one 58 connected by passages 87, 89 to the venturi 14 and the other 59 by passages 80, 81, 82 with the air scoop 12. The chambers 58, 59 communicate by a calibrated passage 90 and the passage 87 is connected with the downstream side of the throttle 15 when closed by a restricted branch 88. A chamber 60 closed by the diaphragm 66 is connected to the unmetered fuel chamber 56 by passages 61 running through spokes 62. A valve 83 operated by a sealed capsule 84 responsive to changes in air temperature and pressure may control the passage 80 to the chamber 59 as shown or the venturi connection to the chamber 58 in such manner as to keep the differential pressure created in the chambers 58, 59 constant for a given mass rate of air flow. The valve 83 may be rendered ineffective by opening a valve 85. The valve 68 is biassed to open position by an adjustable spring 75 and has a strainer 76 and a float-operated vent valve assembly 77 on its inlet side. The chamber 56 is connected by passages 92, 94 and the chamber 57 by passages 98, 99 to the metering unit 29. The metering unit 29 comprises a chamber 91 fed from the passage 92 past a valve 93 connected to and opened progressively with the throttle. The chamber 91 may be connected with a chamber 95 through one or more metering jets. Thus, the " automatic lean " jet 105 communicates with the chamber 95 by a chamber 106 and ports 107, 108, whilst an " automatic rich " jet 113 is similarly connected by a passage 112 and ports 114, 115. For high power output, a "power-enrichment " jet 109 is provided, but this is only effective when a diaphragm actuated valve 117 is opened on the attainment of a predetermined pressure difference between the passage 92 and the chamber 106. The ports 107, 108, 114, 115 as well as the end of the venting passage 94 are controlled by a three-lobe disc 96 operated by a lever 97. A valve 100 controlling the filling passage 99 is opened by a cam 101 operated by the lever 97 and is open in all except the " idle cut-off " position of the latter. In both the full rich " (Fig. 3) and " automatic rich " positions of the lever 97 all the ports and the valve 100 are open, but in the former the valve 85 which is operated from the lever 97 is also open. In the " automatic lean " position the ports 114, 115 are closed and in the " idle cut-out " position all the ports and the valve 100 are closed. The chamber 95 is connected by the passage 30 with the injection pump 31. The fuel control valve 68 may be arranged downstream of the metering unit 29. The fuel injection pump 31, Fig. 7 (see Group XXVIII), comprises a number of plungers 127 actuated through tappets 125 by a swash-plate 124 journalled on an engine-driven member 121. The latter is coupled to the driving gears by an Oldham coupling 122 with a locating pin to prevent incorrect assembly. Springs 129, 131 maintain the plungers and tappets in contact. Each plunger 127 has a central bore 146 communicating with an inlet annulus 147 and a discharge annulus 148. The plunger is shown at the end of its stroke with the annulus 148 connected by a further annulus 169 with the pump reservoir 159. The moment of fuel injection is determined by adjustable byepass sleeves 149 which cut off the annulus 147 from the reservoir 159 at a certain point in the stroke of the plunger. The fuel passes a check valve 166 and through passages 167 on its way to the pipes 32. The sleeves 149 are adjustably connected to a plate 152 carried by a piston 153 urged in one direction by a spring 154 and in the other by a rod 155 connected to the diaphragm 46 by a lever 156. The size of the diaphragm 46 and the strength of the spring 154 may be so chosen that the pressure in the pump reservoir 159 either increases or decreases as the air and fuel flow increases. The accelerator pump 52 comprises a diaphragm 49 urged by the vacuum in the pipe 53 against a spring 51 to draw fuel into a chamber 175 through orifices 176, 177, the latter of which is directed against the diaphragm 46. On acceleration, the vacuum is reduced and extra fuel is discharged through the orifices 176, 177, some of it aiding the movement of the diaphragm 46. The pump reservoir 159 is provided with a bead type filter 160, a float-operated vent valve 163 and a venturi 161 to draw off vapour trapped above the upper plunger 127. Where two fuel injection pumps are supplied from the same pipe 30, their deliveries may be made and maintained equal by connecting their levers 156 by an adjustable linkage, Fig. 8 (not shown). The byepass sleeves 149 may be arranged to control the end of injection instead of the beginning. In a modification (Fig. 9, not shown), the diaphragm acts on the piston 153 through a push-rod only. This arrangement comprises two diaphragms of different size, the venturi or other pressure being admitted to the space between the diaphragms and the fuel pressure being applied to the remote faces of the diaphragms. The accelerator pump is arranged coaxially with these diaphragms. In another modification (Fig. 11, not shown), an increase in fuel pressure reduces the effective stroke of the pump and an increased air flow tends to close the fuel control valve. In two further modifications (Figs. 12, 13, not shown), the effective stroke of the pump is controlled manually and the throttle is controlled automatically to maintain a constant proportion of air to fuel by a diaphragm subject on one side to the pressure in the metered fuel chamber or other point downstream of the fuel control valve and on the other side to the pressure of a spring and to atmospheric, air scoop, venturi or other desired pressure. In one of these forms increasing air flow tends to open the fuel control valve and increasing fuel pressure tends to close the throttle whilst in the other form the same effect is obtained by reversing both these arrangements. Specifications 577,007 and 611,402 are referred to.